Cover Page - USD ($)
12 Months Ended
Dec. 31, 2019
Feb. 13, 2020
Jun. 28, 2019
Cover page.      
Document Type 10-K    
Document Annual Report true    
Document Period End Date Dec. 31, 2019    
Document Transition Report false    
Entity File Number 001-36014    
Entity Registrant Name AGIOS PHARMACEUTICALS, INC.    
Entity Incorporation, State or Country Code DE    
Entity Tax Identification Number 26-0662915    
Entity Address, Address Line One 88 Sidney Street    
Entity Address, City or Town Cambridge    
Entity Address, State or Province MA    
Entity Address, Postal Zip Code 02139    
City Area Code 617    
Local Phone Number 649-8600    
Title of 12(b) Security Common Stock, Par Value $0.001 per share    
Trading Symbol AGIO    
Security Exchange Name NASDAQ    
Entity Well-known Seasoned Issuer Yes    
Entity Voluntary Filers No    
Entity Current Reporting Status Yes    
Entity Interactive Data Current Yes    
Entity Filer Category Large Accelerated Filer    
Entity Small Business false    
Entity Emerging Growth Company false    
Entity Shell Company false    
Entity Public Float     $ 2,563,418,196
Entity Common Stock, Shares Outstanding   68,513,573  
Documents Incorporated by Reference Portions of the registrant’s definitive proxy statement for its 2020 Annual Meeting of Stockholders to be filed pursuant to Regulation 14A within 120 days of the end of the registrant’s fiscal year ended December 31, 2019 are incorporated by reference into Part III of this Annual Report on Form 10-K to the extent stated herein.    
Document Fiscal Year Focus 2019    
Document Fiscal Period Focus FY    
Amendment Flag false    
Entity Central Index Key 0001439222    
Current Fiscal Year End Date --12-31